The most pessimistic predictions of sea level rises as ice sheets are melted by global warming may have to be scaled back as a result of an extraordinary discovery that ice persisted when the Earth was much hotter than today.
Scientists have discovered that glaciers survived for hundreds of thousands of years during an extraordinary era when crocodiles roamed the Arctic and the tropical Atlantic Ocean was as warm as human blood.
They had thought that Earth was ice free during the so called Turonian period, a “super greenhouse world” between 93.5 million and 89.3 million years ago. But now evidence has been found of hothouse glaciers that persisted by studies of tiny plankton and other marine organisms.
Read the rest of the Telegraph article here.
I was hoping to link to a BBC website article, but they don’t seem to find it newsworthy.
Read the article in Science magazine, if you have a subscription, or the abstract if you don’t:
Isotopic Evidence for Glaciation During the Cretaceous Supergreenhouse
André Bornemann,1,2* Richard D. Norris,1 Oliver Friedrich,1,3 Britta Beckmann,4 Stefan Schouten,5 Jaap S. Sinninghe Damsté,5 Jennifer Vogel,1 Peter Hofmann,4 Thomas Wagner6
The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon, with tropical sea surface temperatures over 35°C. High-amplitude sea-level changes and positive 18O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New 18O data from the tropical Atlantic show synchronous shifts 91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap. Even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets, calling into question the common assumption that the poles were always ice-free during past periods of intense global warming.
1 Scripps Institution of Oceanography, University of California, San Diego, Geosciences Research Division, 9500 Gilman Drive, La Jolla, CA 92093–0244, USA.
2 Institut für Geophysik und Geologie, Universität Leipzig, Talstraße 35, D-04103 Leipzig, Germany.
3 School of Ocean and Earth Science, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK.
4 Institut für Geologie und Mineralogie, Universität Köln, Zülpicher Straße 49a, D-50674 Köln, Germany.
5 Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, Post Office Box 59, 1790 AB Den Burg, Texel, Netherlands.
6 School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
There are new and conflicting discoveries all the time, there is still a lot we probably don’t understand about the future of the earth and the influence of the greenhouse effect.
In fact me way worry about the wrong things, better understanding would probably be reached in few years after more research is done about the past and the current changes.
Can Polar Ice Sustain Global Warming?
New discoveries about the behavior of glaciers in the Turonian period may indicate that polar Ice didn’t disappear from the face of the earth in times that were considered to be of a supergreenhouse world.
The most pessimistic predictions of sea …
Hi Paul, I haven’t got a subscription, haven’t read the entire article, but a couple of questions:
I assume the icesheets were at the poles and at high altitudes? Was there a much greater temperature differential then between the poles and tropics? Where the IPCC models originally predicting that warming would be uniform over the globe – but now predicting more warming at the Arctic relative to the rest of the planet?
Paul: 1) How deep was the longest ice core?
2) How old is the modern ice cap at its base?
“The results from the study are consistent with other studies from Russia and New Jersey that show sea level fell by about 25-40 m (82-131 ft) at the same time that the ice sheets were growing during the Cretaceous period. Sea level is known to fall as water is removed from the oceans to build continental ice sheets; conversely, sea level rises as ice melts and returns to the sea.
The presence or absence of sea ice has major environmental implications, specifically in terms of sea level rise and global circulation patterns. As humans continue to add large amounts of carbon dioxide and other greenhouse gases that accelerate the heating of the atmosphere and oceans, research on Earth’s past climate conditions is critical to predict what will happen as Earth’s climate continues to warm”
http://www.sciencedaily.com/releases/2008/01/080110144824.htm
That fact “Ray” John (QLD) claims “Reality trumps model-based predictions” by highlighting his selection from the abstract is not surprising
You state that:
“But now evidence has been found of hothouse glaciers that persisted”
The ABSTRACT states that
“The Turonian (93.5 to 89.3 million years ago) ”
or about 4 million years,
“show synchronous shifts 91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap”
“Which, if one pays attention and does not distort, means that about in the middle of this four million year period an ice cap formed for about 200,000 or 0.2 MY and then went away.”
A very different thing from your claim.
Eli/Josh – I haven’t made any claims yet – the text/links are to the Daily Telegraph and Science. The paper is sitting on my pc desktop at work, unread:
PALEOCLIMATE: More Climate Wackiness in the Cretaceous Supergreenhouse?
Richard A. Kerr
Science 11 January 2008: 145.
On page 189 of this week’s issue of Science, paleoceanographers present new data that make the case for polar ice at the height of the Cretaceous hothouse 90 million years ago.
Sorry Charlie, you said:
“But now evidence has been found of hothouse glaciers that persisted”
The evidence shows that the glaciers did not persist, but rather that they reformed for a short period in the middle of the Cretaceous houthous
As to what Kerr said in his appreciation of the article by Bornemann et al;
“Bornemann and his colleagues take the 200,000-year-long isotopic spike as a sign that an ice sheet existed then with at least half the volume of the modern Antarctic ice sheet.”
So there IS a major difference. There is evidence of ice at the south pole for a relatively short time during the Cretaceous. There is no evidence that it persisted throughout the four million year warm period. BTW, as Kerr points out the modelers also have problems getting it warm enough that crocs could survive at the poles where their fossils have been found.
I haven’t read the paper yet, but the abstract is pretty unambiguous – as usual this isn’t proof of anything, just evidence.
Any up to date peer reviewed publications authored by Kerr on the subject would be interesting.
I marvel at the double standards. Proxies and models have been rubbished on this site many times.
Yet here we have a paper describing the world as it was some 90M years ago being held up as evidence of some sort.
Go figure
“They’ve done it exactly right,” says paleoceanographer Timothy Bralower of Pennsylvania
State University in State College. “This is a provocative paper. It’s going to stir it up again.”
“I’ve been a doubter of this whole business [of Cretaceous ice] for a long time,” says paleoceanographer Richard Norris of Scripps Institution of Oceanography in San Diego, California, who is second author on the paper. But as their data came in, “I began to be
more of a believer. Still, I’m not prepared
to say we’ve nailed it.”
Gavin
Just found this thread, I think the ice core that goes back the farthest is 980000 years taken over a number of years. Will try and find a link and post soon.